My question is really not about the heat itself. Let me clarify. Suppose we are using heat pump hot water heater which sources air from inside the home, you are going to extract 2000 BTU's of energy from the air using the equivalent of 1000 BTU's of electric. You have put 2000 BTU's into the water tank and have expended the equivalent of 1000 BTU's of energy to do it.

My question is about the 1000 BTU's, if this is regular air compressor we have stored the mechanical energy and can use it to drive an air tool. In a closed system like a heat pump that doesn't occur. Also note I realize some of the electric is going to be transformed to heat from the motor, friction and unless it was all being transformed to heat we can ignore those points for this discussion.

If it can't drive an air tool where has the equivalent of 1000 BTU's gone.

Let's take this step further, an air compressor could be considered closed system too. The high side is the tank and low side is the atmosphere.

If it can't drive an air tool where has the equivalent of 1000 BTU's gone.

Let's take this step further, an air compressor could be considered closed system too. The high side is the tank and low side is the atmosphere. Me thinks that's a Stretch

In both cases where has the equivalent of 1000 BTU's gone?

Explain what mechanical task a HP does. Because there is NEVER ANY pressure either added or removed from the closed refrigerant loop.Pressure is only re-proportioned within the closed refrigerant loop.

Nothing mechanical added nothing mechanical taken away.

I'm having a hard time understanding your position...maybe this will bring it out.

If we go to using ratios again, increase the ratio up higher from the 1:2, please.

McGiever wrote:\Because there is NEVER ANY pressure either added or removed from the closed refrigerant loop.[/color]

The same thing is true for atmosphere, when you compress the gas into the tank you have reduced atmospheric pressure globally. When you have let it out you have increased it. Granted this a infinitesimally small amount of pressure.

I'm having a hard time understanding your position...maybe this will bring it out.

I don't have a position here, I'm trying to understand where the mechanical energy goes.

franco b wrote:If the mechanical energy is converted to heat then why does that not occur in regular air compressor?

Because of the different design the energy is stored as both heat and compressed air. The heat soon dissipates. When released the air again takes on heat from the surrounding air, cooling it, just like the heat pump cycle.

If we were to suppose the heat pumps for hot water heaters are 200% efficient over standard electric there is only two things that can occur here.

1)You are going to use mechanical energy with the equivalent of 1000 BTU's of heat to extract 2000 BTU's of heat from the air. That's 3000 total . Net result is 2000 BTU's of usable heat and that 1000 BTU's of mechanical energy is wasted to somewhere.

2)You are going to use mechanical energy with the equivalent of 1000 BTU's of heat to extract 1000 from the air and the mechanical energy is converted to heat. Net result is 2000 BTU's of usable heat.

Just to note again I realize some of that 1000 BTU's will be transformed to heat because of friction etc. That is really not relevant to the discussion.

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The reason for my question is simple, if number one is occurring then using these hot water heat pumps inside a home in cold weather climate is not a very good idea.

Richard S. wrote:1)You are going to use mechanical energy with the equivalent of 1000 BTU's of heat to extract 2000 BTU's of heat from the air. That's 3000 total . Net result is 2000 BTU's of usable heat and that 1000 BTU's of mechanical energy is wasted to somewhere.

I don't think that is correct. 1000 BTU is converted to mechanical energy in order to extract an additional 1000 BTU from the air for 2000 total. The mechanical energy has been converted back to heat less any losses.

To prove it I think you would need a sealed well insulated room of known cubic air content and measure the temperature drop of the air to determine the BTU loss of the air.

If those heat pump hot water heaters use about half the electricity of a standard electric water heater, that would confirm it also.